This disclosure relates to ram air turbines utilized to provide emergency power for an aircraft. More particularly, this disclosure relates to biasing assemblies within a ram air turbine that supplies both electric and hydraulic power to an aircraft.
A ram air turbine is used to generate supplemental power in an aircraft by extracting power from an air stream along the exterior of the aircraft during flight. The ram air turbine includes a turbine that drives an electric motor or hydraulic pump. In operation, the turbine is moved from a stowed position within the aircraft to a position that provides clearance for blades of the turbine and the aircraft. The turbine is mounted at the end of a strut and drives a turbine drive shaft that in turn drives the electric motor or hydraulic pump.
The ram air turbine may experience extreme loads, such as during high level, short duration events (HLSDs). Biasing members of the ram air turbine can become damaged during such events. During an aircraft engine blade loss event, the severe HLSD vibrations occur first as the engine spools down. Then, as it continues to turn due to air loads, a high unbalance load continues to drive the longer duration windmilling vibrations. Either or both of these vibrations could significantly reduce the fatigue life of ram air turbine components without measures to limit impact loading.